The present invention relates to an electrostatic pump, and more specifically, to electrostatic pumps that use an electrostatically actuated diaphragm to pump fluids.
Some industrial, commercial, aerospace and military systems depend critically on reliable pumps for fluid (including gas) handling. Among recent trends in the art of pumping fluids is the increasing use of micro- and meso-pumps. Micro- or meso-pumps are relatively small devices that often use an electrostatic force to move pump walls or diaphragms. The electrostatic force is often applied by applying a voltage between two paired electrodes, which are commonly attached to selected pump walls and/or diaphragms. The electrostatic force results in an attractive force between the paired electrodes, which moves the selected pump walls or diaphragms toward one another resulting in a pumping action.
A limitation of many such devices is that the fluid being pumped often moves between the paired electrodes. The dielectric, conductive, polar or other properties of the pumped fluid can affect the performance of the pump, and in particular, the electrostatic force between the paired electrodes. This may reduce the efficiency and/or reliability of the pump. In addition, the electric field applied between the paired electrodes can impact or change the properties of the fluid being pumped. This may be undesirable in some applications. For these and other reasons, it would be desirable to provide a electrostatically actuated pump that avoids passing the fluid through the electric field of the pump.
The present invention includes methods and devices for electrostatically pumping fluids without passing the fluids through the electric field of the pump. In one illustrative embodiment, this is accomplished by providing an elastic diaphragm within a pumping chamber of an elementary pumping cell. A first side of the diaphragm may be exposed to the fluid during pumping, while the other side may be positioned adjacent a stationary electrode that, in an illustrative embodiment, is mounted on or near the opposite chamber wall. The diaphragm preferably has an electrode that is in registration with the stationary electrode.
During use, the diaphragm is preferably deflected toward the stationary electrode via an electrostatic force between the stationary electrode and the electrode on the diaphragm. In one illustrative embodiment, this draws the pump fluid from an inlet port of the pumping chamber along the first side of the diaphragm. When the electrostatic force is removed, the restoring elastic force of the diaphragm may push the fluid drawn into the pumping chamber through an outlet port in the pumping chamber. This may be repeated to provide a continuous pumping action, if desired. In some embodiments, check valves may be provided on the inlet and/or outlet ports to enhance the pumping action. Such check valves may be provided separately, or by the diaphragm if desired. Some other embodiments perform pumping action without a need for check valves, which can be difficult to design and operate at low flows or low pressures.
In another illustrative embodiment, two or more of the elementary pumping cells discussed above may be used in concert to provide a pumping action. In this embodiment, an elementary pumping cell may include two pumping chambers separated by a separating wall. The two pumping chambers are preferably in fluid communication with one another through a port in the separating wall. Each of the pumping chambers preferably has an elastic diaphragm that lies along the separating wall in an un-activated state.
Like above, each diaphragm preferably has an electrode that is separated from a stationary electrode, which in an illustrative embodiment, is mounted on or near the opposite wall of the corresponding pumping chamber. To help improve the efficiency and/or operation of the pump, it is contemplated that the opposite wall of each pumping chamber may be curved so that the stationary electrode is located closer to the electrode on the corresponding diaphragm near the edges of the pumping chamber, if desired.
During use, a voltage may be applied between the stationary electrode of a first one of the two pumping chambers and the electrode of the corresponding first diaphragm. This deflects the first diaphragm toward the stationary electrode of the first pumping chamber via an electrostatic force, which in the illustrative embodiment, causes the pump fluid to be drawn into the first pumping chamber between the first diaphragm and the separating wall. At the same time, a similar voltage may not be applied between the stationary electrode of the second pumping chamber and the electrode on the second diaphragm. The restoring elastic force of the second diaphragm then closes the port between the two pumping chambers.
Next, a voltage may be applied between the stationary electrode of the second pumping chamber and the electrode of the second diaphragm. This deflects the second diaphragm toward the stationary electrode of the second pumping chamber via an electrostatic force, causing the pump fluid to be drawn through the port in the separating wall and into the second pumping chamber between the second diaphragm and the separating wall. At the same time, the voltage between the stationary electrode of the first pumping chamber and the electrode on the first diaphragm may be reduced or eliminated. The restoring elastic force of the first diaphragm may help push the fluid through the port in the separating wall, and into the second pumping chamber. The movement of the first diaphragm may also close the inlet port of the first pumping chamber.
Next, the voltage between the stationary electrode of the second pumping chamber and the electrode of the second diaphragm may be reduced or eliminated. This may cause the restoring elastic force of the second diaphragm to push the fluid through an outlet port of the second pumping chamber. The elastic force of the first diaphragm may help keep the port in the separating wall closed. This sequence may be repeated to provide a continuous pumping action. It is contemplated that multiple elementary pumping cells may be used together in a similar way, if desired. In addition, various other embodiments are contemplated for pumping fluids without passing the fluids through the electric field of the pump, some of which are described below.